Reclamation of its post-industrial engineered films is becoming a key priority at film extruder Raven Industries Inc., Sioux Falls, S.D.
As the company adds film extrusion capacity, it will rely even more on a new, sophisticated, custom-built reclaim system by ADG Solutions LLC, Fairfield, Conn. The line is up and running and the workhorse system is earning its keep. Officials aren't willing to disclose the amount of the original investment but the system was designed to reprocess up to 15 million pounds of resin annually. Think about a configuration that will process more than 3,000 pounds per hour of polyethylene reclaim that has complexity woven into its layers with construction including string polyester reinforcements. All of the material that is reclaimed is produced by Raven; the company does not have immediate plans to reclaim film from third-party sources.
Raven Industries has been a long-standing producer of highly engineered textiles for covering and lining applications. Its agricultural products are used, for example, to cover an acre at a time of silage that needs protection from winter weather. Other applications include geomembranes and covering materials for a variety of other applications in construction and environmental and industrial film markets.
The extensive engineering required and the experimental runs of such complex materials invariably lead to high levels of so-called industrial scrap, which is to say production-related scrap for startup, shutdown or trial runs that has never gone out into the customer's hands.
Raven management decided it was unacceptable in business and environmental terms to send such high levels of scrap to the local landfill, and began to investigate what they could do about it.
"Raven has been committed to improving sustainability over the last few years. Enhancing our recycling practices was a logical next step for us," says Anthony Schmidt, VP and GM of the engineered films division. The result was the design and implementation of a sophisticated material-recovery system that provided for essentially all of Raven's waste to be reprocessed in a recycling line for producing pellets that could subsequently be coextruded into its primary products.
Raven meets the need for its primary wide-area film products with a dozen blown and cast film extrusion lines that can deliver materials with up to nine layers and thicknesses from 0.30 to 80 mils. Within the last 18 months, one of its equipment installations was a seven-layer oriented barrier system from Davis-Standard LLC, Pawcatuck, Conn. That seven-layer die configuration was designed for further nine-layer expansion.
In November, Raven acquired Integra Plastics Inc., Madison, S.D., which also is in the process of increasing capacity through facility expansions at several of its locations.
Clearly, the company isn't slowing down its film production and therefore, its reclaim system had to be designed to keep up with the demand.
ADG Solutions, acting as a system sales, designer and integrator, put together a custom recycling system that was specific to Raven's needs, which were, to say the least, complex. President and industry veteran Sandy Guthrie, in coordination with Raven management, provided PMM with information about the machinery and technology involved in the recycling system.
For Guthrie and ADG, the requirements to reclaim film that ranged from 10 to 80 mils thick with a polyester string reinforcement was a new challenge. Developing a system that could process that material and, if desired, move the polyester string as an unmelt, required the use of equipment not normally used in typical reclaim lines, says Guthrie.
"This required configuring the conveyors to handle very light to heavy scrap," explains Guthrie. "The shredder needed to have a special program installed to cut this reinforced material; the extruder needed a special screw design; the self-cleaning filter needed to handle [a] large amount of unmelt and contamination; and the pellet at the end of the line had to be conditioned to be able to go to day bin, gaylord or outside to a silo at temperatures well below zero degrees [Fahrenheit] in winter at a controlled heat and moisture level."
Recycling complex film structures
All of the recycling operations take place in a building directly adjacent to Raven's primary production systems. The operation virtually eliminates any need to deliver scrap to the landfill.
An Epic III system from Davis-Standard controls the entire operation. It is a custom designed and manufactured Windows-based PLC control system developed exclusively for the control of extrusion systems. Specific equipment used by the Raven system is as follows, along with details about power requirements that give a sense of its magnitude.
In-feed is accomplished via a 48-inch-wide conveyor with a tunnel-type, all-metals detector with an oversized aperture opening.
Shredding is done with a WLK 15E system from Weima America Inc., Fort Mill, S.C. A Weima control panel controls the volume of material discharged from the shredder so as to maintain proper feed to the conveying system.
Material is conveyed forward on a drag slide discharge conveyor, which is followed by a surge conveyor with another metal detector.
Extrusion system disconnect panels include loads from extruders, melt pump, vacuum pump, pelletizer system minus the dryer, the second screen changer, and the barrel heaters.
The first extruder on the system is a ram machine from Davis-Standard. It is 6-inch diameter, 24-1 length-to-diameter with 600 horsepower, water cooled and capable of feed rates above 3,000 pounds per hour. The screen changer from Fimic/ADG, Tucker, Ga., is independently controlled and can operate in a continuous or pressure mode. The filter will filter out various contaminants from a piece of metal to the polyester string. The screen will last between 3,000 and 4,000 cleanings, which are typically every 10 to 15 minutes. The melt pump from Maag Automatik Inc., Charlotte, N.C., meters the material to a melt pipe system and to the hot melt extruder that allows the melt to devolatize through the use of a shower-head die. These strands are exposed to atmosphere allowing complete devolatization of the materials to avoid traditional venting that's prone to overflow. The second-stage Davis-Standard hot melt extruder is 165mm at 24-1 L-D and rated at 400 horsepower.
At the discharge end of the second extruder is a 6-inch slide plate screen changer from Nordson Xaloy, New Castle, Pa. There is a hydraulic diversion valve to divert the flow during startup to enable quick starts. Gala Industries Inc., Eagle Rock, Va., supplied the underwater pelletizer system with a dryer that prepares the pellets for delivery to the fluid bed cooler and classifier system. The cooler and classifier system was provided by Witte Pumps & Technology LLC, Lawrenceville, Ga.
At the end of the recycling line, the process delivers the pellets to holding hoppers, and then to gaylords. The gaylords are weighed, stickers are printed to time-stamp and record the weight of each gaylord, and the appropriate sticker affixed to its matching gaylord.
Merle R. Snyder, senior correspondent
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